It is known to use stacked blocks to create retaining walls. These blocks may have a tapered shape, so that they can be fitted together in a curve. One popular product is the MASSBLOC® retaining wall system, which utilises tapered blocks with a facetted front profile.
Some models, such as the KEYSTONE® planter unit, contain cavities, which reduce the weight of each block, and can be filled with soil to hold vegetation, improving the aesthetic qualities of the wall. Blocks of this general type are disclosed in U.S. Pat. Nos. 5,601,384, 6,622,445, 6,701,687, and 4,920,712.
One major problem with existing blocks is that the centre of mass is located towards the front of the block, reducing the stability of the retaining wall. The MASSBLOC® retaining wall system comprises two types of blocks—a base block for the bottom layer of a wall, and a standard block that has a lip protruding from the lower back edge of the block, which fits behind the block below to ensure that the blocks on each layer are the same distance back from the layer below. However, this requires the use of two different types of blocks in constructing the retaining wall, with the accompanying inefficiencies and increased costs.